Finger clip pulse oximeter

ABSTRACT

The invention is directed to Apparatus for measuring a physical parameter, such as the saturation percentage of oxygen in blood. The pulse oximeter is built into the finger clip, and therefore the device is small, lightweight and very portable, as well as more reliable.

FIELD OF THE INVENTION

This invention relates generally to medical instrumentation, and moreparticularly to a finger clip sized pulse oximeter for measuring andindicating the percentage of one or more constituents of arterial blood.

BACKGROUND OF THE INVENTION

Pulse oximetry devices in the past have utilized a sensor, generallyattached to the finger, which is conductively coupled to an electronicdevice which actually measures and indicates the percentage of thedesired constituent of arterial blood.

Examples of pulse oximeters using a conductively attached sensor wouldinclude U.S. Pat. Nos. 5,279,295; 5,035,243; 5,217,012; 5,249,576;5,245,003; 5,209,230; 5,170,785; 5,080,098; 5,069,213; 5,041,187;4,971,052; 4,964,408; 4,928,691; 4,865,038; 4,830,014; 4,825,879;4,825,872; 4,770,179; 4,700,708; 4,553,498, and 4,621,643.

Applicant also has a patent on a pulse oximeter which utilizes aconductively attached sensor, U.S. Pat. No. 4,773,422, reissued as RE.33,543. The entire contents of U.S. Pat. No. 4,773,422, issued Sep. 27,1988 are hereby incorporated by reference. Applicant's patent pulseoximeter is embodied in several products, including the Model 8600Portable Pulse Oximeter and the Model 8500 Hand Held Pulse Oximeter.

Despite achieving great commercial success with its line of pulseoximeters, applicant has recognized several problems with existing pulseoximeters, including their own. First, the units are still very bulkyand difficult to easily transport from one location to another. Theseunits are typically bought from patient to patient, rather than being ina stationary location. Applicants' units, particularly its hand heldmodel 8500 are often used in connection with ambulances and are movedabout a great deal. Secondly, the flexible conductive cable used by allexisting pulse oximeters to attach the sensor frequently gets damageddue to being wrapped around the pulse oximeter unit during transportfrom one location to another. Despite many failsafes built into thecable at either end, over time the cable connections fail.

What is needed is a more portable compact pulse oximeter whicheliminates the flexible conductive cable connecting the sensor to thepulse oximeter.

SUMMARY OF THE INVENTION

Applicants' have invented a pulse oximeter which incorporates theelectronic processing component and the display into the sensor itself,eliminating the need for a separate component attached to the sensor bya flexible conductive cable. This finger clip pulse oximeter isextremely small, lightweight and durable compared to existing pulseoximeters. It is so small and lightweight that it can be carried aroundthe users neck like a whistle. The inventive finger clip pulse oximeteris battery operated.

The finger clip itself operates like existing finger clips, having anupper and lower portions which are pivotally connected such that as afinger is inserted into the finger clip, the two portions lift apart andpivot to evenly grip the finger. When a finger is inserted into thefinger clip pulse oximeter, the device automatically turns fully "on",measures, calculates and displays the measured saturation percentage ofO₂ (SpO₂) on a small display carried on the finger clip.

These and other advantages and features which characterize the inventionare pointed out with particularity in the claims annexed hereto andforming a further part hereof. However, for a better understanding ofthe invention, its advantages and objects obtained by its use, referenceshould be made to the drawings which form a further part hereof, and theaccompanying descriptive matter, in which there is illustrated anddescribed a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE FIGURES

In the drawings, wherein like reference numerals represent like partsthroughout the several views:

FIG. 1 is a side view of the inventive finger clip pulse oximeter;

FIG. 2 is a front view of the inventive finger clip pulse oximeter;

FIG. 3 is a top view of the inventive finger clip pulse oximeter;

FIG. 4 is a bottom view of the inventive finger clip pulse oximeter;

FIG. 5 is a perspective side view showing a finger being inserted intothe finger clip;

FIG. 6 is a perspective side view of the inventive finger clip showingthe finger fully inserted into the finger clip;

FIG. 7 is an exploded perspective side view of the inventive fingerclip;

FIG. 8 is a perspective side view showing the spring disengaged from thelower housing

FIG. 9 is a perspective view showing the two housings unconnected fromeach other;

FIG. 10 is an alternative embodiment of the inventive pulse oximeter inwhich the invention is contained in a single housing, which is contouredto accept a finger pad pressed against the housing;

FIG. 11 is a front view showing another alternative embodiment of theinventive pulse oximeter in a single housing contoured for the forehead;

FIG. 12 is a side view of the embodiment of FIG. 11;

FIG. 13 is an alternative of the spring of the preferred embodiment;

FIG. 14 is a generalized block diagram of the pulse oximeter circuitry;

FIG. 15 is a circuit board layout of the top side of the circuit board;

FIG. 16 is a circuit board layout of the bottom side of the circuitboard;

FIG. 17 is a detailed circuit schematic of the pulse oximeter circuitry;

FIG. 18 is a flowchart of the program which monitors photodiodemeasurements and fully turns "on" the pulse oximeter, and

FIG. 19 is a flowchart of the program which turns the pulse oximeter"off".

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein specific preferred embodiments of theinvention. This description is an exemplification of the principles ofthe invention and is not intended to limit the invention to theparticular embodiments illustrated.

Referring now to FIGS. 1-4, the preferred embodiment of the finger clippulse oximeter is shown generally at 10. Finger clip pulse oximetertakes the form of first and second housings 12 and 14, which areinterconnected with spring 16. Spring 16 has ends 18 and 19 which fitinto two holes 20 and 21 on either side of the second housing 14. Spring16 is comprised of two generally U-shaped spring elements, which arethemselves connected in a side by side manner with a short springelement section 22, as is best seen in FIG. 7. As can be seen best inFIGS. 1 and 4, spring element 22 fits into groove 24 of the bottom ofthe first housing. Housing 12 has indents 26 and 28 which pivotallyreceive the tabs 30 and 32 of housing 14. Spring 16 allows the twohousings 12 and 14 to pivot and/or separate relative to one another.Cord 34 is optionally provided to allow the finger clip pulse oximeterto be hung around the neck of the user.

FIG. 2 shows opening 36, which is formed by the contours provided in thetop of the first housing 12 and the bottom of the second housing 14.Opening 36 receives the inserted finger, and the finger clip pulseoximeter pivots and separates to grippingly receive the finger andposition the pulse oximeter 10 for reading the pulse and blood oxygensaturation of the patient.

FIG. 3 shows the top view of the finger clip pulse oximeter 10 in whichreference numeral 38 indicates the display which displays the sensed anddetermined pulse and blood oxygen saturation of the patient (SpO₂), eachbeing positioned next to their respective legend 40 and 42. Perfusionindicator 44 is a multicolored LED which flashes green with each pulseamplitude when the reading is within a normal range (percent modulationof infrared light is more than 0.24%), flashes red when the pulseamplitude is too small (percent modulation of infrared light is lessthan approximately 0.08%), and flashes yellow (by turning on both thegreen and red simultaneously) when the pulse amplitude is marginal.Raised ridges 46 and 48 are provided to better aid in holding thedevice.

Finger clip pulse oximeter 10 is very portable due to its light weightand small size. The preferred embodiment weighs approximately 2.2 ouncesand its dimensions are approximately 1.3 inches wide by 1.3 inches highby 2.2 inches long.

Referring now to FIGS. 5, finger clip pulse oximeter 10 is shown withthe second (or upper) 14 housing pivoted with respect to the first (orlower) housing 12 to enlarge opening 36 to enable insertion of thefinger of a patient. Spring 16 provides an urging force which forces thetwo housings to the closed position shown in FIG. 1.

Referring now to FIG. 6, after the user releases the finger clip pulseoximeter from the position shown in FIG. 5, the spring 16 causes the twohousings 12 and 14 to uniformly grip the inserted finger. Depending onthe size of the inserted finger, spring 16 can lift the U-shaped springend of the second housing, causing the two housings to separate from oneanother.

Referring now to FIG. 7, an exploded side perspective view of thepreferred embodiment of the inventive finger clip pulse oximeter 10 isshown. The upper or second housing is shown generally at 14. Referencenumeral 50 is a two sided surface mounted circuit board which containsthe electronic circuitry for determining the pulse and blood saturationlevel; drives the display LED's; drives the radiation emitting LED's;drives the indicator 44 and controls the photodiode which measures theradiation received from the radiation emitting LED's. Circuit board 50will be discussed in more detail below. Opening 52 in the bottom of thesecond housing provides access to the radiation emitted by the radiationemitting LED's which is received by the photodiode mounted on the bottomside of the circuit board 50 (discussed further below). Circuit board 50is electrically connected to the first housing, shown generally at 12via ribbon cable 54 which allows power and control signals to be sentbetween the two housings. First housing also holds batteries 56 whichare used to power both the two radiation emitting LED's 58 and 60 andcircuit board 50. Opening 62 in the top of the first housing allows theradiation emitted by LED's 58 and 60 to be directed towards thephotodiode opening 52. In the preferred embodiment, the two openings 52and 62 are positioned directly opposite each other.

Referring now to FIG. 8, spring 16 is shown unconnected to the firsthousing 12. Spring 16 is designed to allow section 22 to be releasedfrom the groove in the bottom of the lower section 12, which allows thespring 16 to pivot around ends 18 and 19. As shown best in FIG. 9, thetwo housings may now be separated for ease of cleaning, since they areonly attached via flexible ribbon cable 54.

It should be understood that the location of the various electronicelements in the preferred embodiment is a matter of design choice. Forexample, the batteries could be located in the second housing, or thecircuit board could be located in the first housing. The only importantconsideration for use with this embodiment (a transmissive type pulseoximeter) is that the photodiode and radiation emitting LED's must be inseparate housings.

Referring now to FIG. 10, by utilizing a reflective type pulse oximeter,for example of the type disclosed in U.S. Pat. No. 5,224,478, all of thecomponents can be located in a single housing 55, either the first orsecond housing, if desired. As is well known in the art, with areflective type pulse oximeter both the photodiode which receives theradiation and the LED's which emit the radiation are located proximateto each other. FIG. 10 shows an alternate embodiment utilizing areflective type pulse oximeter, in which the pulse oximeter is housed ina single housing. Rather than using the two housings to act as a fingerclip, the user simply presses the pad of their finger against thecontoured surface to obtain the reading.

Similarly, FIG. 11 and 12 show another alternate embodiment of the pulseoximeter which uses a reflective type pulse oximeter housed in a singlehousing which is contoured to form fit to the forehead of the patient.

FIG. 13 shows an alternate embodiment of spring 16 which includes anadditional loop in the U of the U-shaped spring elements for additionalresiliency.

Referring now to FIGS. 14 through 17, the electronic circuit board 50 isdiscussed in greater detail. The electronic circuit board is describedgenerally in connection with the block diagram in FIG. 14. Thecorresponding circuit board layout, both top and bottom, are shown inFIGS. 15 and 16 and the corresponding detailed schematic diagram isshown in FIG. 17. In lieu of describing the invention's operationrelative to the detailed circuitry, the following description willproceed with respect to the generalized block diagram of FIG. 5, withperiodic mention, as necessary, to the corresponding FIGS. 15-17.

The microprocessor is shown at block 70 (circuit element U1), which is asingle chip microprocessor, a Motorola MC68HC705C8FN in the preferredembodiment, contains its own one time programmable read only memory(OTPROM) and RAM. The programming, shown at reference numeral 72,discussed in FIGS. 18-19 is stored in the OTPROM memory contained insidethe single chip microprocessor. The two radiation emitting LED's areshown at blocks 74 and 76 and are controlled by the microprocessor. Thephotodetector is shown at block 78 (circuit element PD1 in FIG. 16) inFIG. 14. The analog circuitry for conditioning the signal received bythe photodetector is at block 80. In the preferred embodiment, theparticular apparatus and method of determining the pulse and bloodoxygen saturation percentage utilize the technique described in U.S.Pat. No. 4,773,422, reissued as RE. 33,643, which will not be discussedin great detail here. It should be understood that any availabletechnique for determining pulse and blood oxygen saturation percentagecan be utilized by the inventive finger clip pulse oximeter.

Power is provided to the microprocessor through the flexible ribboncable 54, shown at block 82 in FIG. 14. The circuit schematic of FIG. 17shows six LED's, which make up the display. These six LED's can be seencarried by the top of the circuit board 50. Three of the LED's are usedto display the pulse measured and three LED's are used to display thesensed and measured saturation percentage of O₂ (SpO₂). The displayportion of the circuitry is shown at block 84 of FIG. 14. Block 85 inFIG. 14 represents the circuitry for controlling the perfusion LED(reference numeral 44 in FIG. 3). Finally, block 86 represents commonlyavailable communications circuitry (not shown in FIGS. 15-17) forproviding for remote display of the pulse or blood oxygen saturationpercentage, either conductively coupled or wirelessly coupled to theremote display.

Referring now to FIG. 18, the flowchart corresponding to the programwhich monitors the photodiode and turns "on ", wakes up or shifts thedevice from a low power mode to a normal operating power mode is shown.Using this program and the apparatus, the inventive pulse oximetereliminates the need for an "on" switch. Block 90 represents apredetermined time interval, one second in the preferred embodiment, atwhich time the device turns fully "on" or "wakes up ", shown at 92sufficiently to emit radiation from one or both of the LED's 58 and 60,represented at block 94. The program measures the photodiode response at94 and determines at 96 whether the light measurement represents anincrease from the maximum measurement reference level, stored by theprogram. If the evaluation is "yes" then the last measured valuereplaces the reference level and the device returns to a low powerstate, shown respectively at 98 and 100. If the evaluation is "no" thenthe program determines at 102 whether the decrease in light measured isa significant decrease from the previous value measured, which is 40 mVwhich represents a 5 times decrease in the preferred embodiment. If thedecrease is not significant the device returns to a low power state at100. However, if the decrease is significant, this is an indication thata finger has been inserted, interfering with the radiation emitted bythe LED's, and therefore turns the device "on" or shifts it to a normaloperating state at 104, which also triggers the pulse and blood oxygensaturation determination and display. Block 102 allows the device to bemoved from a lighter area to a darker area without triggering the deviceto wake up, and thereby waste power.

For the embodiments which utilize the reflective type pulse oximeter,the program would be modified to monitor for a significant increase inlight rather than a significant decrease, since no light would bereflected unless a finger or other body part, such as a forehead, wherein place.

Referring now to FIG. 19, the flowchart corresponding to the programwhich monitors the photodiode and turns "off", puts to sleep or shiftsthe device from a normal operating power mode to a low power mode isshown. Block 90, once per second, is determined by the microprocessortiming. Block 94 is the same as in FIG. 18. In order to determine whento put the device to sleep, the program evaluates the light measured bythe photodiode to determine if is within a predetermined threshold valuecompared to the maximum reference value discussed above, shown at block110. In the preferred embodiment the threshold value would be 2 times(2X) or 50%. If the measured light is not within the permitted rangecompared to the maximum the timer (block 90) is reset for 10 seconds,shown at block 112, since this is an indication that the finger,forehead etc. is still in place and the device is still operating. Ifthe measured light is within the permitted range, and remains so for atleast 10 seconds, shown at block 114, the maximum reference is reset,shown at block 116, and the device is returned to sleep, turned off, orput in its low power mode at block 118. If the measured light is notwithin the permitted range for 10 seconds (block 114), this indicateslight level fluctuations. The program continues to monitor for twominutes (block 120) and if it does not receive good data during thosetwo minutes, i.e. 10 seconds within the permitted range, the device isput to sleep, otherwise the device continues to measure the lightreceived by the photodiode every second.

The above Examples and disclosure are intended to be illustrative andnot exhaustive. These examples and description will suggest manyvariations and alternatives to one of ordinary skill in this art. Allthese alternatives and variations are intended to be included within thescope of the attached claims. Those familiar with the art may recognizeother equivalents to the specific embodiments described herein whichequivalents are also intended to be encompassed by the claims attachedhereto.

What is claimed is:
 1. Apparatus for measuring the blood oxygensaturation of arterial blood inside a body portion, comprising:grippingmeans for releasably gripping a body portion, wherein the gripping meansis comprised of finger gripping means for releasably gripping a finger;a pulse oximeter means for sensing and determining the blood oxygensaturation of the arterial blood inside the gripped body portion, thepulse oximeter means being completely carried by the gripping means; adisplay means for displaying the sensed and determined physicalparameter, the display means being attached to the gripping means; powermeans for providing power to the pulse oximeter means and the displaymeans; and program means operatively connected to the pulse oximetermeans and display means for sensing the presence of a finger andswitching the apparatus from a low power state to a normal power state.2. The apparatus of claim 1 wherein the program means senses the absenceof a finger and switches the apparatus from a normal power state to alow power state to conserve power.
 3. The apparatus of claim 2 includingtransmission means for transmitting the determined blood oxygensaturation level to a remote display.
 4. The apparatus of claim 3wherein the transmission to the remote display is wireless.
 5. Theapparatus of claim 1 wherein the program means switches the apparatusfrom a normal power state to a low power state after a predeterminedtime interval to conserve power.
 6. Apparatus for measuring the bloodoxygen saturation of arterial blood inside a body portion,comprising:gripping means for releasably gripping a body portion,wherein the gripping means is comprised of finger gripping means forreleasably gripping a finger, wherein the finger gripping meanscomprises:a first housing; a second housing; and pivot meansinterconnecting the first and second housings for allowing the first andsecond housings to pivot relative to one another to releasably grip afinger inserted between the first and second housings, the pivot meansbeing constructed and arranged to allow the first and second housings toseparate from one another, wherein the pivot means urges the twohousings towards each other, thereby applying pressure to releasablygrip the finger inserted between the first and second housings andwherein the pivot means is a spring means comprised of two generallyU-shaped spring elements, each generally U-shaped spring element havingan upper end and a lower end, the two lower ends being connected in aside by side manner a predetermined distance apart by an elongate springelement such that the two generally U-shaped spring elements arepositioned on either side of the first and second housings and orientedsuch that the open end of the generally U-shaped spring elements facesin the same direction as the finger receiving ends of the first andsecond housings, and wherein the upper ends of the spring means arepivotally attached to the sides of the first housing and the elongatespring element is releasably received by a groove in a bottom of thesecond housing, whereby the first and second housings pivot and separaterelative to one another to grippingly receive a finger inserted betweenthe first and second housings, and where the first and second housingsmay be unconnected from one another for ease of cleaning by releasingthe elongate spring element from the groove in the bottom of the secondhousing, enabling the spring means to pivot around its upper ends: apulse oximeter means for sensing and determining the blood oxygensaturation of the arterial blood inside the gripped body portion, thepulse oximeter means being completely carried by the gripping means; anda display means for displaying the sensed and determined physicalparameter, the display means being attached to the gripping means. 7.The apparatus of claim 6 wherein each generally U-shaped spring elementincludes an additional loop to increase the resilience in the springmeans.
 8. A pulse oximeter, comprising:a housing having a portion of itsouter surface contoured to receive the forehead of a patient pressedagainst the housing; pulse oximeter means for sensing and determiningthe blood oxygen saturation of the arterial blood inside the forehead,the pulse oximeter means carried by the housing and furthercomprising:radiation emitting means for directing radiation of at leasttwo discrete wavelengths through the arterial blood inside the forehead;photosensor means for intercepting radiation reflected by the arterialblood inside the forehead; computation means for determining the bloodoxygen saturation level, connected to the photosensor means; power meansfor providing power to the radiation emitting means and a display means,and a display means carried by the housing for displaying the bloodoxygen saturation level determined by the pulse oximeter means.
 9. Apulse oximeter, comprising:pulse oximeter means for sensing anddetermining blood oxygen saturation in the arterial blood in a bodyportion, the pulse oximeter means being in a normally low power state,and wherein the pulse oximeter means is constructed and arranged forsensing and determining the blood oxygen saturation in the arterialblood of a forehead; and power conservation means operatively connectedto the pulse oximeter means for sensing the presence of the body portionand which switches the pulse oximeter from a low power state to a normalpower state, whereby the pulse oximeter means senses and determines theblood oxygen saturation in the arterial blood in the body portion.
 10. Amedical device of the type being housed in first and second housings,each housing being generally rectangular shaped having back, front, top,bottom and side ends and wherein the two housings are connected by apivot means such that the two housings are stacked one on top of theother, the improvement comprising:a pivot means wherein the pivot meansis a spring means comprised of two generally U-shaped spring elements,each generally U-shaped spring element having an upper end and a lowerend, the two lower ends being connected in a side by side manner apredetermined distance apart by an elongate spring element such that thetwo generally U-shaped spring elements are positioned on either side ofthe first and second housings and oriented such that the open end of thegenerally U-shaped spring elements faces towards the front wall of theends of the first and second housings, and wherein the upper ends of thespring means are pivotally attached to the sides of the first housingand the elongate spring element is releasably received by a groove inthe bottom of the second housing, whereby the first and second housingsmay be unconnected from one another for ease of cleaning by releasingthe elongate spring element from the groove in the bottom of the secondhousing, enabling the spring means to pivot around its upper ends. 11.Apparatus for measuring a physical parameter, comprising:gripping meansfor releasably gripping a body portion; electronic means for sensing anddetermining a physical parameter, carried by the gripping means; powermeans for providing power to the electronic means, and non-mechanicalautomatic on/off means operatively connected to the electronic meanswhich non-mechanically senses the presence of a body portion gripped bythe gripping means and switches the apparatus from a low power state toa normal power state, whereby the apparatus senses and determines thephysical parameter.